1. Field of the Invention
This invention relates generally to the field of molding.
More particularly, this invention relates to apparatus and methods for molding hardenable material.
In a further and more specific aspect, the present invention relates to an apparatus and method for molding hardenable material.
2. Prior Art
Plastics or resins, in the modern meaning of the word, are generally defined as materials capable of being formed into usable products by heating, milling, molding, and similar processes. Resins are both natural and synthetic. However, synthetic resins comprise the foundation of an enormous range of products the growth of which shows no signs of abating.
The distinction between plastics and resins is at best arbitrary, since many of today's synthetic materials can properly be called both resins and plastics. Historically, it appears that the term resin was applied to those products primarily used as substitutes for the natural product in coating compositions, whereas the term plastic was applied to designate those compositions that involved a molding operation in their fabrication.
The characteristic ability of most plastics to soften but not melt when heated, so that their shape can be changed under mechanical stress without losing cohesion, producing a rigid new form upon cooling, is a property resulting from their molecular structure. Plastics are composed of giant molecules, known as polymers, with immensely long chains of repeating units derived from short molecules; in the case of addition polymers the short molecules are known as monomers. The chains are built up by formation of chemical bonds. When heated, these chains move apart sufficiently to permit them to slide over one another but retain their cohesiveness due to the forces that hold the polymeric chains together.
This ability to slide into new positions, which are retained on cooling, is the basis of plastics fabrication processes, such as molding or extrusion of sheets or other forms from heated granules, vacuum forming of sheets into desired forms, blowing of extruded tubes into bottles, and other processes. At higher temperatures, maximum mobility is attained allowing injection molding, a process in which the plastic is injected into a hollow casting and cooled thus taking the shape of the hollow casting. These processes require only moderately high temperatures, usually in the range of 300-400.degree. F., and are very versatile enabling easy fabrication of an infinite variety of forms.
Injection molding normally involves rendering plastic material fluid in a chamber outside of a mold cavity and then forcing the fluid plastic into the mold cavity under pressure. The mold is cooled and split, two halves being locked during molding and opening automatically or manually after a volume of liquefied plastic has filled the mold cavity. The cooled article is then ejected from the mold cavity and the process repeated.
In its simplest form, an injection molding machine may include a heated barrel with a hydraulically operated ram, an opening in the rear of the barrel being fitted with a hopper into which measured amounts of plastic pellets or granules are fed. Falling in front of a plunger, the pellets are forced under high pressure into a heating section of the barrel, pushing out an equivalent volume of molten plastic into the mold cavity which then cools and hardens to take the shape of the mold cavity. Consistent with conventional practice, a typical mold is normally comprised of two mold halves that may be clamped together to bound a mold cavity, the two mold halves being clamped together and at a pressure that resists that exerted by the plastic entering the mold cavity. A hydraulic ram, a hydraulically operated toggle mechanism or other equivalent mechanism may achieve this. The process of injection molding plastic is generally similar to processes for injection molding other hardenable or otherwise moldable materials such as metal and perhaps other materials that may generally soften or take the form of a fluid when heated and a solid when cooled.
As previously mentioned, conventional injection molding apparatus operate to conduct pressured molten of fluid material into a mold cavity. Because the molten material is provided under pressure, the molten material is normally turbulated when it enters the mold cavity. However, if molten material is turbulently introduced into the mold cavity, it will flow discontinuously and will not fill the mold cavity at a steady rate. As a result, the molded article may not have a uniform mechanical strength over its mass and may not have sufficient pressure resistance.
Furthermore, plastic injection molding methods currently involve processes for introducing artwork during the molding process to impart the artwork with a molded article. To this end, skilled artisans normally locate films bearing selected artwork within a mold cavity prior to the molding process. The artwork, of which may be comprised of a selected artistic design, symbols, words, letters or other potential forms of indicia, is normally provided as ink located on at least one surface of the film. In this regard, a turbulent flow of molten plastic impacting the indicia on the film may distort and mar the appearance of the indicia. As a result, common methods of imparting indicia to a molded article during the injection molding process typically involve directing the artwork away from the flow of molten plastic so that the finally molded article will have the indicia on an external surface thereof. The inherent deficiency of having indicia on an external surface of a molded article is that it can become damaged over a period of time. This is especially true with molded articles that experience high levels of use or wear such as molded plastic elements found in combination with mobile phones, calculators and other similar items.
The prior art has provided a variety of apparatus and systems operative for facilitating laminar flow into a molded cavity. However, current apparatus and systems are expensive and structurally challenging to implement and construct. Furthermore, current methods of injection molding have not been able to remedy the problems associated with successfully and efficiently imparting indicia with a molded article during the injection molding process. To the contrary, existing methods that introduce molten plastic to inked surfaces or surfaces having indicia normally necessitate treatment steps to the article subsequent to the injection molding process to correct the distortion of the indicia such as trimming off portions of the article where distortion is present.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide a new and improved mold apparatus for molding hardenable or otherwise moldable material.
Another object of the present invention is to provide a mold apparatus that is easy to construct.
And another object of the present invention is to provide a mold apparatus that is inexpensive.
Still another object of the present invention is to provide a mold apparatus that provides laminar flow of hardenable or otherwise moldable material into a mold cavity.
Yet another object of the instant invention is to provide a mold apparatus that is efficient.
Yet still another object of the instant invention is to provide a new and improved method of filling a mold cavity with hardenable or otherwise moldable material.
And a further object of the invention is to provide a method of filling a mold cavity that is easy and inexpensive to implement.
Still a further object of the immediate invention is to provide a method of filling a mold cavity that is efficient.
Yet a further object of the invention is to provide a new and improved method of molding an article from hardenable or otherwise moldable material.
And still a further object of the invention is to provide a method of molding an article that conserves and eliminates the potential waste of hardenable or otherwise moldable material throughout the molding process.